Catalysts have been used widely in the refining and chemical processing industries for many years. Hydroprocessing catalysts, including hydrotreating and hydrocracking catalysts, are now widely employed in facilities worldwide. Used or “spent” hydroprocessing catalysts discharged from these facilities typically contain metal components such as molybdenum, nickel, cobalt, vanadium, and the like in the form of complex metal sulfides.
In order to recycle catalytic metals and provide a renewable source for the metals, efforts have been made to extract metals from spent catalysts, whether in supported or bulk catalyst form. US Patent Publication No. 2007/0025899 discloses a process to recover metals such as molybdenum, nickel, and vanadium from a spent catalyst with a plurality of steps and equipment to recover the molybdenum and nickel metal complexes. U.S. Pat. No. 6,180,072 discloses another complex process requiring solvent extraction as well as oxidation steps to recover metals from spent catalysts containing at least a metal sulfide.
Shales, especially those that contain appreciable quantities of organic carbon, have long been known to be enriched with a variety of transition metals in the form of complex metal sulfides, especially sulfides of Mo, Ni, Co, Cu, Cr, V, Pb, U and Ag. Mineralogical studies have revealed a variety of these metal sulfides in shales of which metal-rich black shales are the most common type.
Molybdenum-rich black shales contain sulfide beds with more than 2% of each of Mo and Ni, about 2% Zn and 200 to 700 mg/t each for Au, Pt and Pd. Ores averaging about 4% Mo and containing up to 4% Ni, 2% Zn and precious metals are recovered in which the Mo-bearing phase is recovered directly from the ore by roasting followed by caustic leaching to produce ammonium molybdate.
Significant mineralization of nickel and molybdenum occur in ore deposits in association with uranium mineralization. Pyrite occurring in the zone of uranium mineralization has been found to contain up to 2 to 4% Ni. Nickel also occurs as millerite, pentlandite and its alteration product violarite, along with the copper sulfides. Molybdenum occurs as molybdenite. The mineral assemblage constitutes a unique hematitic uranium-nickel-molybdenum sulfide ore.
There is a need for an improved and simplified process to recover metals including but not limited to molybdenum, nickel, cobalt and vanadium, from complex metal sulfide ores treated by crushing, grinding, screening, flotation and the like known beneficiating techniques to produce a bulk concentrate from which the molybdenum can be separately recovered from the nickel and other metals.